Technical data

214 Web Tools Administrator’s Guide
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IPsec concepts
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FIGURE 42 AH header in transport mode and tunnel mode
Encapsulating Security Payload
ESP provides authentication, and also provides privacy by encrypting the IP datagram. The use of
an ESP header is similar to the use of the AH header. A hash algorithm is used to calculate an
authentication value, the authentication value is sent in an IP datagram, and the same hash
algorithm is used by the receiver to verify the authentication value. ESP can be used in either
transport mode or tunnel mode, as shown in Figure 43.
FIGURE 43 ESP header in transport mode and tunnel mode
Basic IPsec configurations
There are three basic configurations for IPsec use:
• Endpoint to Endpoint
• Gateway to Gateway
• Endpoint to Gateway